The present invention relates to a shaft-equipped grinder used in a mold-graving device, in which the shaft of the grinder can be easily and quickly located on the mold-graving device and driven thereby at high rotational speed.
A shaft-equipped grinder is used in a mold-graving device for polishing and grinding the mold. Conventional shaft-equipped grinders include grinding wheel, grinding paper ring, grinding paper disc and iron brush wheel. Depending on the grinding effect and subject to abrasion, the shaft-equipped grinder must be frequently replaced. Therefore, it is necessary to frequently disassemble and assemble the shaft-equipped grinder on the mold-graving device.
FIG. 1 shows a conventional shaft-equipped grinding wheel 1 which includes a grinding member 12 with a circular periphery and a shaft 11 axially extending from the center of the grinding member 12. In order to avoid loosening and radial displacement of the shaft, which will result in that the grinding member 12 hits the work piece and breaks, it is necessary to accurately locate the shaft 11 on the mold-graving device coaxially with the rotary shaft of the motor.
FIG. 2 shows the fixing device for the mold-graving device, in which a pneumatic motor 21 is axially disposed in the main body 2 of the mold-graving device. The rotary shaft 22 of the motor is screwed with a sleeve tube 23 having two opposite plane faces 24. A claw-like cylinder clamp 25 is disposed in the sleeve 23 and an outer sleeve 26 is screwed around the sleeve tube 23 to fasten the cylinder clamp 25 for clamping the shaft 11 of the grinding wheel 1. In addition, the outer periphery of the outer sleeve 26 is formed with two opposite plane faces 261 for a tool to tighten the outer sleeve 26 so as to avoid axial detachment or radial rotation of the shaft 11.
According to the above arrangement, the fixing device can accurately fix the grinding member on the mold-graving device coaxially with the rotary shaft of the motor. However, when disassembling or assembling the grinding member, as shown in FIG. 3, an operator must use two wrenches 27 at the plane faces 24, 261 of the sleeve tube 23 and the outer sleeve 26 to reversely twist the same so as to tighten or untighten the cylinder clamp 25. Apparently, it is quite inconvenient to disassemble or assemble the grinding member. Moreover, due to negligence, the shaft 11 of the grinding member may be not accurately tightened. This will lead to slippage or even flying out of the grinding member during working.
In addition, in order to cooperate with the shaft-equipped grinder, the following parts of the mold-graving device in addition to the rotary shaft 22 are required to be concentrically processed at high precision: the portion of the sleeve tube 23 screwing with the rotary shaft 22, the inner edge of the sleeve tube 23 for fitting with the cylinder clamp 25, the outer edge of the cylinder clamp 25 for fitting with the sleeve tube 23, the inner edge of the cylinder clamp 25 for contacting with the shaft 11 of the grinding member and the portion of the outer sleeve 26 for fastening the cylinder clamp 25. Obviously, it is difficult to process these parts and the manufacturing cost is very high.
FIG. 4 shows an electric screwdriver head 3 which is used in a pneumatic screwdriver or wrench for quickly assembling or disassembling from the tool. However, such tool works at lower rotational speed so that the concentricity of the screwdriver head 3 and the power outputting rotary shaft of the tool is not required to have high precision. Therefore, such structure cannot be applied to the shaft-equipped grinding member.